By further developing a well-known measurement method to be suitable for industrial use, a team at the Fraunhofer Institute for Physical Measurement Techniques IPM has now succeeded in implementing highly sensitive gas sensor technology in a robust and compact format—at a fraction of the previous cost. Their efforts have earned the researchers the Joseph von Fraunhofer Prize for 2026.
The photoacoustic effect has been known for over 150 years: Gases exposed to light heat up. Pulsing the light generates periodic pressure fluctuations, i.e., sound waves, the frequencies of which can be uniquely assigned to individual gases. This photoacoustic effect forms the basis for a measurement method that is highly precise even at low gas concentrations. Despite its high sensitivity, the method has previously only occupied a niche, primarily because it relies on a resonator for acoustic amplification. This resonator is highly sensitive to even the slightest changes in air pressure, temperature or mechanical stress. However, ensuring an accurate measurement requires that the system precisely hits the correct resonant frequency.
A light-emitting diode makes all the difference
This is precisely where the team led by Christian Weber, Katrin Schmitt and Johannes Herbst from Fraunhofer IPM has now achieved a breakthrough. The researchers have developed a sensor principle that employs a small light-emitting diode to continuously determine its own resonant frequency and automatically adjust the optical excitation accordingly.
The team thus made a virtue out of necessity: “The sensor wall absorbs radiation and generates a strong photoacoustic signal. This was thought to be a drawback, but we reconsidered: Maybe it’s a feature!” “We are now using this wall in combination with a second light source to quickly measure the resonant frequency,” says Christian Weber, project manager in the Integrated Sensor Systems group at Fraunhofer IPM.
The resonant amplification thus remains stable at all times, even under fluctuating conditions. At the same time, the minimal hardware requirements enable sensor prices that are roughly one-tenth of those for conventional devices.
Successful market launch with leak detection
The first major application demonstrates the effect of this simplification: Schütz Messtechnik is already using the technology for inspecting natural gas networks. The tiniest fractions of methane in the air must be detected here in order to identify leaks at an early stage.
“The measurements are now very fast and precise due to the small measurement chamber volume of roughly four milliliters instead of the four liters previously required,” stresses Johannes Herbst, project manager in the Spectroscopy and Process Analytics group at Fraunhofer IPM. “Their small size also makes these systems significantly more portable and versatile.”
Another area of application: In gas-insulated high-voltage systems, the new sensor technology enables continuous, integrated monitoring of the quality of the insulating gas for the first time—a key prerequisite for reliable monitoring and enhanced operational safety.
Bundled expertise for technology transfer
This rapid time-to-market was made possible by the close collaboration between Christian Weber, who was recently awarded the 2025 Hugo Geiger Prize for his doctoral thesis on photoacoustics, Katrin Schmitt, Head of the Thermal Measurement Techniques and Systems group, and Johannes Herbst, who contributed his laser spectroscopy expertise to facilitate the technology transfer. The team was supported by many colleagues who contributed greatly to the success of the solution.
The award-winning sensor principle serves as an example of the technological impact of excellent research. Katrin Schmitt is pleased: “It’s always great when you can look at a finished product and say: ‘There’s a part of Fraunhofer in there.’” The methane sensors are only the beginning, as many other applications of resonant photoacoustics are already foreseeable. These range from industrial process monitoring to environmental monitoring along busy roads. Its robust, selective and cost-effective operation gives this technology the potential to fundamentally transform gas sensing.
